Recently, there has been known a self-propelled cleaner provided with a movement unit for autonomously cleaning a floor surface while autonomously moving with a predetermined movement pattern. There has also been developed a type of the self-propelled cleaner capable of reducing remaining dust which is left without being removed from the floor surface, even if dust is concentrated on a specific place in a room (for example, Patent Document 1).
FIG. 19 is a block diagram illustrating a self-propelled device 201 described in Patent Document 1. The self-propelled device 201 includes a dust detection unit 202 detecting dust on a floor surface, a movement unit 204, a mode control unit 206 instructing a predetermined movement pattern, a movement control unit 205 controlling the direction of the movement of the movement unit 204, and a measuring unit 203 measuring a distance to an obstacle. When the dust detection unit 202 detects dust on a surface to be cleaned, the self-propelled device 201 changes the movement pattern of the mode control unit 206 such that the self-propelled device 201 carefully moves around the part where dust is detected, and then, returns to a normal operation. Patent Document 1 describes a unit, as the dust detection unit 202, in which a light-emitting unit and a light-receiving unit are mounted on a suction unit 208 which sucks dust on the surface to be cleaned. This unit detects a dust amount by detecting that light emitted from the light-emitting unit is intercepted when dust passes between the light-emitting unit and the light-receiving unit.